Ignition system for internal combustion engines



Nov. 30, 1965 MoALLlsTER 3,221,116

IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed July 24, 1962 I L 26 L INVENTOR DON M. MCALLISTER ATTORNEY United States Patent 3,221,116 IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES Don M. McAllister, Wethersfield, Conn., assiguor of onehalf to Chester J. Later, Wethersfield, Conn. Filed July 24, 1962, Ser. No. 211,972 7 Claims. (Cl. 200-27) This invention relates toswitching devices for internal combustion engines and is concerned primarily with improvements in the construction and operation of the breaker points.

There have been many efforts in the past to maintain a constant gap between the breaker points of internal combustion engines over a long period of time and to provide proper sparking conditions at both starting speeds and operating speeds of such engines, but thus far such proposals have involved such inadequate or incomplete solutions to the problems as to preclude their adoption in practice.

It is among the objects of the present invention to provide a switching device for internal combustion engines comprising a mounting plate providing spaced pivots, a relatively rotatable shaft extending beyond the plate and carrying cam means, a pair of arms mounted on the pivots respectively, and providing followers engaging the cam means, the arms carrying cooperating contacts which are successively closed and opened during rotation of the shaft to provide a gap dimension substantially independent of wear between the cam means and followers. Means for adjusting the contacts to set the dimensions of the gap are contemplated and it is preferred that means be provided for biasing the followers toward the cam means. The followers preferably engage the cam means at circumferentially spaced positions relative to the shaft. According to a preferred embodiment of the invention, each arm carries a pair of contacts to produce a pair of gaps, rotation of the shaft successively opening and closing such gaps. The contacts carried by each arm in such an embodiment are preferably relatively rigidly fixed against relative movement once they have been adjusted.

The invention contemplates a pair of independently movable arms mounted on pivot means and providing follower-s engaging the cam means, each of the arms carrying a pair of contacts to produce a pair of gaps, rotation of the shaft successively opening and closing the gaps.

It is also contemplated that a first pair of electrically interconnected contacts be carried by the plate in predetermined spaced relationship in association with a breaker arm pivotally carried by the plate, a follower carried by the arm, a second pair of electrically interconnected contact-s carried by the arm in predetermined rigidly spaced relationship cooperating with the first contacts respectively, to define first and second gaps, and cam means carried by the shaft engaging the follower and successively opening and closing the gaps. In such a case the first pair of contacts are preferably mounted on a second arm pivotally carried by the plate.

By virtue of the present invention, a more efiicient operation is assured and a longer life is imparted to the breaker points themselves as well as to the entire ignition system. Maintenance time and cost are also greatly reduced in conjunction with installations incorporating the present invention.

A more complete understanding of the invention will follow from a description of the accompanying drawings wherein:

FIG. 1 is a fragmentary plan view depicting one form of the present invention;

FIG. 2 is a fragmentary plan view of a modified form of the invention; and

FIG. 3 is a fragmentary plan view of a further modified form of the invention.

3,221,116 Patented Nov. 30, 1965 In each of the modifications depicted in the drawings, the low voltage side of a conventional ignition circuit has been depicted diagrammatically in conjunction with the switching device. In each case, one terminal 10 of the switching device is connected to ground through a conductor 12 while the other terminal 14 is connected by a conductor 16 to one side of the primary winding 18 of an ignition coil 20, the other end of the winding being connected by a conductor 22 to the vehicle battery 24 which is connected in series with an ignition switch 26 to ground.

Extending beyond a conventional mounting plate 28 is a conventional rotatable shaft 30 carrying a conventional cam 32 depicted, for purposes of this description, as having six lobes.

Referring to FIG. 1, a bracket assembly 34 is composed of a first bracket member 36 and a second bracket member 38 adjustably secured together by a screw 40 extending through an opening in the bracket member 36 and through a slot 42 in the bracket member 38, with a nut, not shown, applied to the opposite threaded end of the screw 40 to maintain the bracket members in a desired predetermined relationship.

The bracket member 36 contains an opening 44 penetrated by a post or pivot member 46 extending upwardly from the plate 28. The bracket member 38 contains a slot 48 in cooperation with a screw 50 received in a threaded opening provided in the plate 28 so as to clamp the bracket assembly in a desired position. A pivot or post 52 extends upwardly from the bracket member 38 to rotatably support an arm 54, between which and the pivot 52 there is interposed an insulating sleeve 56. Adjacent the free end of the arm 54 there is secured a follower or rubbing block 58 maintained in engagement with the cam 32 by means of a leaf spring 60 in a conventional fashion. On a surface of the arm 54 opposite the follower 58 there is secured a breaker point 62, and in spaced relationship with the breaker point 62, another breaker point 64 is carried by a rigid extension 66 of the arm 54. It is important that there be a minimum of resiliency in the extension 66 so that for all practical purposes, the breaker points 62 and 64 will be maintained in mutually fixed relationship.

Another breaker arm 68 is pivotally mounted on the pivot 46 with an intervening insulating sleeve 70 and at its free end carries a follower or rubbing block 72 biased towards the cam 32 by means of a leaf spring 74. An extension 76 of the arm 68 projects into the gap provided by the spaced breaker points 62 and 64, and on its opposite surfaces carries breaker points 78 and 80 cooperating respectively with breaker points 62 and 64 to provide multiple gaps for the ignition system which are successively opened and closed as the shaft 30 rotates and the cam 32 displaces the followers 72 and 58. Starting from the position depicted in FIG. 1, as the shaft 30 rotates clockwise as indicated by the arrow, the arm 68 will move counterclockwise causing the points 62 and 78 to separate, at the same time moving the points 80 and 64 towards contacting positions. Then the arm 54 will begin to move clockwise about its pivot 52, moving the point 64 away from the point 80 and the point 62 towards the point 78. This combined movement of the two arms is preferably timed so that the initial break between the points 62 and 78 will occur prior to head dead center of the power stroke being controlled and so that the break between the points 64 and 80 occurs beyond head dead center of that power stroke so as to provide an extended ignition period so as to promote more uniform combustion. It is important that the points 62 and 64 be rigidly mounted with respect to one another and that the points 78 and 80 be rigidly mounted with respect to one another so that there will be no resilient bounce which would otherwise occur at elevated speeds. In this way the gap between the points 62 and 78 will close sooner than otherwise so as to increase the dwell period during which the coil 20 is being saturated in advance of the next discharge. The closing of the second gap between the points 64 and 80 partially removes the charge from the capacitor 82 that occurred during the opening of the points 62 and 78, thereby extending the life of the points constituting the first gap defined by the points 62 and 78. The dwell of the points 64 and 80 of the second gap will be shorter than that of the points of the first gap so that the charge placed upon the capacitor 82 by the second gap is less and the adverse effect on the points of the first gap will be less, assuring them a longer life. It is contemplated that the followers 58 and 72 will wear equally so as to maintain the gaps uniform throughout the life of the points. This will greatly extend the life of the points and will also result in uniformly efiicient operation of the engine. The initial size of the gap in each case will be adjusted by manipulation of the screws 40 and 50 and by either bending the extension 66 or by adjusting the initial distance between the point 64 and the point 80 in some other suitable fashion that will assure relative rigidity between the points 64 and 62 once the setting has been effected.

The modification depicted in FIG. 3 differs from that of FIG. 1 in the elimination of the second gap defined by the points 64 and 80 of the modification shown in FIG. 1. Otherwise the structure, operation and advantages parallel those described with reference to FIG. 1.

Referring to FIG. 2 of the drawings, a bracket 84 provides an upstanding post or pivot 86 over which an arm 88 is disposed with an intermediate insulating sleeve 90 for pivotal mounting of the arm. The arm carries a follower or rubbing block 92 of insulating material biased towards the cam 32 by means of a leaf spring 94. The free end of the arm 88 carries opposed breaker points 96 and 98 which cooperate respectively with breaker points 100 and 102 rigidly secured in spaced relationship on a fixed portion of the bracket 84. Whereas the breaker point 102 is adjustably mounted with respect to the bracket 84 by means of a screw 104, once it has received its desired adjusted position, it is then rigid relative to the breaker point 100. The bracket 84 is secured to the mounting plate 28 by means of screws 106 and 108 received in slots 110 and 112 respectively so as to produce a prescribed gap dimension. In this case, when the follower 92 begins to wear, the gap between the points 96 and 100 will become smaller and the dwell will increase, producing a higher saturation of the coil and a greater charge on the condenser. As this is occurring, the gap defined by the breaker points 98 and 102 will increase and even though it no longer closes completely, the higher charge on the condenser will bridge this gap to produce a progressively greater spark to compensate for the decrease in the dimension of the gap occurring between the points 96 and 100.

Whereas the present invention has been described with reference to a very limited number of forms, the appended claims contemplate such variations as will be suggested by the present disclosure to those skilled in the art.

I claim:

1. A switching device for internal combustion engines comprising a mounting plate providing spaced pivots, a

relatively rotatable shaft extending beyond said plate and carrying cam means including a plurality of cam surfaces, a pair of arms mounted on said pivots respectively and providing followers engaging said cam means, said followers lying in the path traversed by said cam surfaces and spaced apart along said path by a distance less than the length of one of said cam surfaces, each of said arms carrying a pair of contacts, each contact of the pair on one arm periodically engaging a contact on the other arm, said contacts defining two gaps which are successively closed and opened during rotation of said shaft.

2. A switching device according to claim 1 including means for adjusting said contacts to set the dimension of one of said gaps.

3. A switching device according to claim 1 including means biasing said followers towards said cam means.

4. A switching device according to claim 1 wherein said followers engage said cam means at circumferentially spaced positions relative to said shaft.

5. A switching device according to claim 1 wherein the contacts are relatively rigidly carried by their respective arms.

6. A switching device for internal combustion engines comprising a mounting plate providing pivot means, a relatively rotatable shaft extending beyond said plate and carrying cam means including a plurality of cam surfaces, a pair of independently movable arms mounted on said pivot means and providing followers engaging said cam means, said followers lying in the path traversed by said cam surfaces and spaced apart along said path by a distance less than the length of one of said cam surfaces, each of said arms carrying a pair of contacts to produce a pair of gaps, rotation of said shaft successively opening and closing said gaps.

7. A switching device for internal combustion engines comprising a mounting plate, a rotary shaft extending beyond said plate, a first pair of electrically interconnected contacts carried by said plate in predetermined spaced relationship, a breaker arm pivotally carried by said plate, a follower carried by said arm, a second pair of electrically interconnected contacts carried by said arm in predetermined rigidly spaced relationship, each contact of one of said pairs periodically engaging a contact of the other of said pairs to define first and second gaps, and cam means carried by said shaft engaging said follower and successively opening and closing said gaps.

References Cited by the Examiner UNITED STATES PATENTS 2,424,626 7/ 1947 Oberdick 200-30 2,674,662 4/1954 Hieger 200-30 2,854,534 9/1958 Beauclair 200-30 2,939,337 6/1960 Sweger 20019 2,987,589 6/ 1961 Mallory 20030 3,048,671 8/1962 Manning 200- FOREIGN PATENTS 1,077,428 4/ 1954 France.

307,955 9/ 1918 Germany.

621,795 11/ 1935 Germany.

BERNARD A. GILHEANY, Primary Examiner. 

6. A SWITCHING DEVICE FOR INTERNAL COMBUSTION ENGINES COMPRISING A MOUNTING PLATE PROVIDING PIVOT MEANS, A RELATIVELY ROTATABLE SHAFT EXTENDING BEYOND SAID PLATE AND CARRYING CAM MEANS INCLUDING A PLURALITY OF CAM SURFACES, A PAIR OF INDEPENDENTLY MOVABLE ARMS MOUNTED ON SAID PIVOT MEANS AND PROVIDING FOLLOWERS ENGAGING SAID CAM MEANS, SAID FOLLOWERS LYING IN THE PATH TRAVERSED BY SAID CAM SURFACES AND SPACED APART ALONG SAID PATH BY A DISTANCE LESS THAN THE LENGTH OF ONE OF SAID CAM SURFACES, EACH OF SAID ARMS CARRYING A PAIR OF CONTACTS TO PRODUCE A PAIR FO GAPS, ROTATION OF SAID SHAFT SUCCESSIVELY OPENING AND CLOSING SAID GAPS. 